Last year around this time my 21 year old Stihl farm boss quit all of a sudden. When I tried to restart it the pull cord wouldn't, and I assumed that the motor had seized. Being an old saw, I decided to just buy a new one. Last week, the cord on the new one quit, and I hoped it was still under warranty (it was a week out) so I took it down to the dealer. When we took it apart the recoil spring had broken, and the spool and cover had partially melted. So I took the old saw down to see if we could steal the parts off of it. In the mean time the guy in the shop found some used parts to fix the new saw with, but while I had the old one there I took the recoil cover off and discovered that the flywheel would turn about halfway before the piston contacted something. We took the muffler off and discovered there was a little rectangular piece of metal inside the cylinder. It turned out to be a piece of the muffler that had been cut against the exhaust manifold after 2 decades of use, and had fallen into the cylinder while I was cutting overhead. I put it back together with a new used muffler and it started right up. I guess I didn't really need a new saw yet, but it never hurts to have an extra.